Portable radiographic unit



Feb. 28, 1961 s. D. REEDER 2,973,435

I PORTABLE RADIOGRAPHIC UNIT Filed Feb. 9,1959

INVENTOR.

S. D. REEDER BYHUJMMQI' A TTORNE Y5 2,973,435 PORTABLE mioemnic in Seth n. Reder, Idaho Falls, who, assignor to Phillips Petroleum Company, a corporation of Delaware Filed Feb. 9, 195;, Ser. No. 792,039

1 Claim. c1. 250*105 This invention relates to portable equipment for use in making radiographs.

As is well known, radiography has longbeen an important tool in the fields of medicine and industry. Powerful X ray machines have been developed which have proved to be very valuable in both these fields. However, X-ray machine represents a sizeable investin'eiit and not readily be transported for use in remote areas. A demand thus exists for simple, portable radiographic equipment which can readily be transported and which does not require a source of electricity for its operation. It is known that radium and other radioactive materials, such as cobalt-60, can be employed as radiographic sources. However, these materials emit radiation at high energy levels so that heavy shields are required.

In accordance with the present invention there is provided a novel portable radiographic unit which utilizes as its radiation source a radioactive isotope that emits electromagnetic radiation at or near the X-ray region. Thulium-170 can be employed to advantage as this radiation source. The unit is constructed in such a manner that the source normally is shielded when the unit is not in actual operation. The apparatus is provided with safety features so that the source is automatically returned to the shielded position when the unit is not in actual operation. The radiographic unit of this invention can be made sufficiently small and light weight that it can be used in remote locations and carried by hand.

Accordingly, it is an object of this invention to provide a novel portable radiographic unit.

A further object is to provide a radiographic unit wherein the radiation source is shielded except when the unit is in actual operation.

Other objects, advantages and features of the invention should become apparent from the following detailed dc scription which is taken in conjunction with the accompanying drawing in which:

Figure 1 is a view, shown partially in section, of the radiographic unit of this invention in its operating position.

Figure 2 is a view taken along line 2--2 of Figure 1.

Figure 3 is a perspective view showing the radiographic unit of this invention in an operating position.

Referring now to the drawing in detail and to Figures 1 and 2 in particular, there is shown a case which is formed of a metal, such as brass. The bottom of case 10 is provided with a circular opening 11 which has a thin metal shield 12 positioned thereacross. The top and sides of the interior of case 10 are lined with a radiation absorption material 13, such as lead. A carrying handle 14 is attached to the top of case 10. A metal block 15 is rotatably mounted within shield 13 on pins 16 and 17. A shutter handle 18 is attached to pin 17 so that block 15 can be rotated within the case. A rod 20 is threaded into block 15 so as to support a radioactive material 21 at a region near the center of block 15. Block 15 is provided with a conical opening 22 which is aligned with opening 11 when the block is in the operating position shown.

7 2,913,435 '7 Patented reb. as. 1961 2 Pins 16 and 11 are located beneath the center of gravity of block 15 so that the block normally is rotated 180 from the position shown. Radiationemitted from source 21 is thus directed upwardly through opening 22 and is blocked by shield 13. when the radiographicunit i s in actual operation, handle 18 is rotated to position the block so that openings 22. and 11 are in alignment. Radiation emitted from source 21 is thus directedout of case 10 through opening 11.v

The radiographic unit of this invention can be made sufiiciently small and light weight that it can readily be carried about and used where needed. A tripod support 25 of Figure 3 can be utilized to position the radiographic unit above an object, not shown, through which the radiation is to be directed. An Xray film holder 26 is positioned beneath the tripod so as to be exposed by the radiation which is emitted downwardly from the portable The object to be studied ispositioned between the radiographic unit and film holder 26-. r

. As previously. mentioned; the radioactive isotope thuliumcan be employed to advantage as the radiation source -in this unit. Thulium-170 has a half life of 127 days and emits gamma rays having energies of 0.084 and 0.053 mev. Thulium is a stable rare earth element which occurs in nature with a mass number of 169. On capturing a neutron, the radioactive isotope thulium-170 is formed which constitutes a source of gamma rays. As specific examples of the operation of this invention, a number of cylindrical pellets of thulium were irradiated in the Materials Testing Reactor at Idaho Falls. These pellets had an average diameter of 0.165 inch and a thickness of 0.65 inch. The average weight of the pellets was approximately 200 milligrams. The pellets were covered with aluminum jackets 10 mils thick and were sealed in quartz tubes and placed in aluminum containers to be irradiated. The pellets were subjected to various neutron dosages and the following activities were observed:

Neutron Average Dosage Neutron Activity (neutrons! Flux (neu- (roentgens/ cm!) trons/cmfl/ hr. at 2") sec.)

2.4X10 21x10 23 4.6Xl0" 1.9X10 35 7.0X10 5.4)(10 65 15.0Xl0 5.6X10 132 25.3)(10 5.9X10 198 across the end of cavity 22. This camera had a total weight of only 28 pounds and its dimensions were approximately 5" X 4" x 5".

Satisfactory radiographics were prepared using this. unit with commercially available X-ray film. Since the radiation from source 21 decreases with time, the use of conventional intensifying screens is often advisable after the source has been in use for some time.

An important feature of this invention resides inthe rotatable source which is mounted such that the source is shielded whenever the unit is not in actual operation. If the unit is left unattended, block 15 automatically rotates 180 from the position shown in Figures 1 and wardly into lead shield 13.

- Although thuliurn-170 is the preferred radiation source,

other radioactive isotopes can also be employed. These 5.27 days 1 M v.

74.4 days 0.316, 0.61 Mev.

1.7 years- 0.08 0.106, 0.06 Mev.

Of these isotopes, Ir-192 is the easiest to prepare because Ir-191 is a naturally occurring stable isotope that can be activated by first order neutron capture.

While the invention has been described in conjunction with a present preferred embodiment, it should be evident that it is not limited thereto.

What is claimed is:

A portable radiographic unit comprising a hollow rectangular parallelepiped formed of a material which serves as a radiation shield, said parallelepiped having a circular opening in the center of the base thereof, a carrying handle secured to and extending from the upper face of said parallelepiped which is opposite the base thereof, a block 'formed of a material which serves as a radiation shield, a source of radioactive radiation positioned at the center of said block, said block having a conical opening therein which diverges outwardly from said source, first and second pins secured to said block on opposite sides thereof and extending outwardly from said block into respective openings in side walls of said parallelepiped so that said pins are free to rotate in said side walls so that said block automatically assumes a first fail-safe position within said parallelepiped whereby said conical opening points upwardly from said base because the center of gravity of said block is below said pins and above said base when said block is in said first position, said upper face of said parallelepiped shielding said source when said block is in said first position, and a second handle secured to one of said pins and extending outside said parallelepiped 'so that rotation of said second handle can rotate said block to a second position inside said parallelepiped whereby said conical opening is in alignment with said circular opening.

References Cited in the file of this patent UNITED STATES PATENTS 2,843,754 Costello July 15, 1958 2,847,581 Clark Aug. 12, 1958 2,860,255 Tumath Nov. 11, 1958 2,891,168 Goertz June 16, 1959 

